Patent application CN 201112225 discloses a trim unit for an electrical switch comprising a trim plate that presents an opening and a control member that is received in the opening.
In that document, a decorative frame is mounted in the opening, at the front of the trim plate, and carries a mounting member for mounting the control member.
However, the presence of the decorative frame spoils the visual uniformity of the trim unit; in addition, the decorative frame has both an attractive purpose and a mechanical purpose, which limits the choice of materials that can be used to make that part.